In countries outside North America, one of the most common causes of hypothyroidism is iodine deficiency. This mineral is an essential component of thyroid hormones. People who do not have natural sources of iodine in their diet, such as fish and other seafood, are at high risk of developing hypothyroidism.
In Canada and the United States, however, the problem has caused by too much iodine in the diet, increased stress levels, anemia, estrogen replacement, birth control pills and medications that block iodine uptake. Excess iodine can result in low thyroid hormone levels by halting the activity of enzymes needed for their production.
There have been cases of people who develop hypothyroidism by taking in too much iodine in the form of iodine-rich seaweed and kelp supplements on a daily basis. Some of this iodine excess may also come from our growing dependence on fast and processed foods, since these foods contribute a generous amount of salt to our daily diet.
Besides iodized salt, other food sources of iodine include seafood, bread, dairy products, plants grown in iodine-rich soil and meat and poultry from animals raised on iodine-rich soil.
The relationship between dietary intake of iodine and thyroid health is complicated; Too little or too much iodine both seem to cause problems.
The thyroid gland always requires the trace element, iodine for the production of thyroxine (T4) but tolerance to iodine supplementation for optimal thyroid function varies from person to person. It’s best to get iodine from good food sources such as sea vegetables (nori, hijiki, wakame, kombu and kelp), sea salt and saltwater fish and seafood.
It’s not unusual for people with suboptimal thyroid function to crave sushi or seafood. If you listen to your body, it will often express its needs for certain nutrients through unusual cravings. Keep in mind that some foods, called goitrogens, can diminish iodine absorption making it unavailable to the thyroid gland in the production thyroid hormones.
Goitrogens are found in cruciferous vegetables such as cabbage, turnips, broccoli, kale and mustard greens), soybeans, peanuts, pine nuts and millet. These are very healthy foods so don’t completely elimininate them just because they contain goitrogens, just to eat them in moderation. Heating these foods also reduces their goitrogenic effects.
Other trace minerals and vitamins that are useful for thyroid health include selenium, B vitamins folate, B6 and B12 and iron. If you are supplementing iron and taking thyroid medications such as Synthroid, please take the two pills a few hours apart as iron reduces the effectiveness of Synthroid.
References
Leslie Beck’s Nutrition Encyclopedia by Leslie Beck, RD. Penguin Books, 2001. Pages 370-272.
The Adrenal Stress Connection by Drs. Karen Jensen and Marita Schauch. Pages 44-46.
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